Owing to the progress of the assembling techniques for electronic apparatuses, the assembling of circuit boards, which constitutes a large portion of the assembling of electronic apparatuses, is carried out by automatically inserting or soldering the electronic components.
Among the surface mounting type chip components, transistors, resistors, small capacitors of less than 1 .mu.F and the like can be easily fabricated in the form of chip, while the radial type aluminum electrolytic capacitor of over 1 .mu.F requires a high technique in fabricating it in the form of chip. Conventionally, when the radial type aluminum electrolytic capacitor is made in the form of chip, it is molded with a resin, and the molding is cured. In the molding and curing process, the characteristics of the capacitor can be altered, the leads can be oscillated, and other defects can occur, thereby making it difficult to obtain a satisfactory result.
As such problems are exposed, various new techniques have been proposed.
FIG. 1 illustrates a chip capacitor consisting of a holder 20 and a radial type aluminum electrolytic capacitor 10. The shape of the interior of the holder 20 is cylindrical, so that it should be suitable to surround the capacitor. On the top of the holder, there is an insulating cover 25 which covers a part of the top of it, and which is integrally formed with the holder 20. Thus a semi-circular opening 24 is provided. A T shaped lead guide 26 having a step is provided on the insulating cover 25, while cut-away portions 27 are formed at the corners of the top portion of the holder 20, the dimensions of the cut-away portions 27 being equivalent to the thickness and width of a pair of leads 13.
Thus the radial type aluminum electrolytic capacitor 10 is inserted from the bottom 23 of the holder 20 into the cylindrical space. The pair of the leads 13 which are drawn over an insulating rubber 11 are bent along the T shaped lead guide 26, and are further bent along the cut-away portions 27, thereby completing the final chip type electrolytic capacitor. Here, the insulating cover 25 serves the function of preventing a short-circuit between the leads 13 and an aluminum cover 12 which is provided on the top of the capacitor 10.
Such a chip capacitor is laid down in the lengthwise posture, and therefore, the contact area between a rear face 22 of the capacitor and the surface of the circuit board is enlarged. Therefore, there is a high probability that the chip capacitor may be laid down over the other electronic components of the circuit board. Accordingly, the setting becomes such that the positional security is not assured. Further, the leads are bent several times, the assembling of the chip capacitor becomes complicated, and a complicated jig for this is required.
Particularly, the total surface 21 of the holder 20 is suction-held by a pneumatic means in order to mount the chip capacitor on the circuit board, and thus, the capacitor is dropped onto the relevant portion of the circuit board. However, the mass of the capacitor is asymmetrically distributed, and therefore, when the dropping is made, the setting cannot be made to the exact position, thereby causing a positional deviation defect. That is, the leads 13 which are bent along the cut-away portions 27 are frequently deviated from the exact position of the circuit board.
Further, when the leads 13 of the above described capacitor are soldered, the opposite side is lifted, and therefore, a particular measure is required for the mechanical oscillations.
FIG. 2 illustrates another conventional chip capacitor. In this device, a holder 40 is installed on the upper portion of the capacitor for drawing leads 33 of an aluminum electrolytic capacitor 30. The holder 40 is provided with a through-hole 41 for drawing out the leads 33 of the capacitor 30, and is also provided with a pair of lead guides 42. The lead guides 42 extend from the through-hole 41 outwardly, and their dimensions are equivalent to the thickness and width of the leads. Further, for the identification of the polarity of the capacitor, one side of it is provided with a projected portion 44, and the other side is provided with a cut face 43.
This capacitor is very simple in its constitution, but the coupling between the capacitor 30 and the holder 40 is very weak. Therefore, the oscillations of the leads are very severe, while it is not provided with a gas discharge hole on the top of the holder for discharging the soldering gas which is produced during the soldering after the surface mounting, thereby producing imperfect solderings.
The common problems encountered in the chip capacitor of FIG. 1 and that of FIG. 2 are as follows. That is, if there are pockmarks or a mass of foreign material near the relevant portion of the circuit board, the soldering becomes imperfect due to the lifting phenomenon of the chip capacitor.